Even though learning fast is clearly indicated in the Conversations of Rav Nahman שיחות הר''ן סימן ע''ו I noticed today the LeM I:74 ליקוטי מוהר''ן חלק א פרק ע''ד where learning with understanding is emphasized. This indicates the sort of compromise that you have in the Litvak world of half the day spent on learning in depth and the second half to be spent on fast learning.